ASET development of at-wavelength phase-shifting point diffraction interferometer

Katsumi Sugisaki; Yucong Zhu; Yoshio Gomei; Masahito Niibe

doi:10.1117/12.472344

1 July 2002 ASET development of at-wavelength phase-shifting point diffraction interferometer

Katsumi Sugisaki, Yucong Zhu, Yoshio Gomei, Masahito Niibe

Proceedings Volume 4688, Emerging Lithographic Technologies VI; (2002) https://doi.org/10.1117/12.472344
Event: SPIE's 27th Annual International Symposium on Microlithography, 2002, Santa Clara, California, United States

Abstract

We have been studying phase-shifting point diffraction interferometry (PSPDI) as a technique evaluating extreme-ultraviolet (EUV) lithographic optics at the working wavelengths. In the PSPDI, the wavefront error of the test optic affects the measurement itself. One of these effects is that flare of a spot focused onto a pinhole of a PSPDI mask is mixed with a test beam as an optical noise. To mitigate the flare effect, we changed the PSPDI mask design and replaced the convex mirror of a test optic. The other effect is reducing the contrast of the interference fringe. To reduce the misalignment of the test optic, we have improved the accuracy of the PSPDI using visible light. Since the residual wavefront error of the test optic is not small enough for at-wavelength PSPDI measurement, we obtained an at-wavelength wavefront using a rather large second pinhole. The obtained EUV wavefront qualitatively agreed with the visible one.

Citation Download Citation

Katsumi Sugisaki, Yucong Zhu, Yoshio Gomei, and Masahito Niibe "ASET development of at-wavelength phase-shifting point diffraction interferometer", Proc. SPIE 4688, Emerging Lithographic Technologies VI, (1 July 2002); https://doi.org/10.1117/12.472344

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